Ceramic matrix composite component having low density core and method of making

ABSTRACT

Disclosed is a ceramic matrix component having a fibrous core and a ceramic matrix composite shell surrounding at least a portion of the fibrous core. The ceramic matrix composite shell comprises a fibrous preform. The fibrous core has a greater porosity than the fibrous preform. A method of making the ceramic matrix component is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/797,123 filed on Feb. 21, 2020, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

Exemplary embodiments pertain to the art of ceramic matrix compositecomponents.

Ceramic matrix composite (CMC) materials have been proposed as materialsfor certain components of gas turbine engines, such as the turbineblades and vanes. Various methods are known for fabricating CMCcomponents, including melt infiltration (MI), chemical vaporinfiltration (CVI) and polymer pyrolysis (PIP) processes. CVI relies oninfiltration to deposit matrix around preform fibers. Infiltration canbe hindered when pores at the surface become filled with matrix beforethe interior. Various approaches have been suggested to address thisissue but new solutions are needed.

BRIEF DESCRIPTION

Disclosed is a ceramic matrix component having a fibrous core and aceramic matrix composite shell surrounding at least a portion of thefibrous core. The ceramic matrix composite shell comprises a fibrouspreform. The fibrous core has a greater porosity than the fibrouspreform.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the fibrous coreporosity is 2-3 times greater than the porosity of the fibrous preform.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the fibrous corefurther comprises ceramic foam.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the ceramic foam ispositioned at a leading edge of the fibrous core.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the ceramic foam ispositioned at a trailing edge of the fibrous core.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the fibrous corecomprises cooling passages.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, cooling passages arelocated at a leading edge of the ceramic matrix component.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, cooling passages arelocated at the trailing edge of the ceramic matrix component.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the ceramic matrixcomposite shell has a thickness greater than or equal to 0.03 inch.

Also disclosed is a method of making a ceramic matrix component. Themethod includes forming a fibrous core having a first porosity, forminga fibrous preform on the fibrous core wherein the fibrous preform has aporosity less than the first porosity, and forming a ceramic matrix onthe fibrous preform using chemical vapor infiltration.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the fibrous corecomprises ceramic foam.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the ceramic foam ispositioned at a leading edge of the fibrous core.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the ceramic foam ispositioned at a trailing edge of the fibrous core.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the fibrous corecomprises sacrificial fibers.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the sacrificial fibersare located at a leading edge of the fibrous core.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the sacrificial fibersare located at a trailing edge of the fibrous core.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a partial cross-sectional view of a gas turbine engine;

FIG. 2 is a perspective view of a CMC component; and

FIG. 3 is a cross sectional view along line 2-2 of FIG. 2 .

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures. The CMC component andmethod of making the CMC component address several needs—the use of afibrous core supports any shorter fibers or plies in the surroundingpreform and composite shell and helps to prevent ply drops and reducesstress resulting from ply drops. Additionally, the greater porosity ofthe fibrous core offers access to the interior of the preform duringCVI. Access to the interior of the preform improves infiltration andresults in a CMC component with more uniform density.

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude other systems or features. The fan section 22 drives air along abypass flow path B in a bypass duct, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through aspeed change mechanism, which in exemplary gas turbine engine 20 isillustrated as a geared architecture 48 to drive the fan 42 at a lowerspeed than the low speed spool 30. The high speed spool 32 includes anouter shaft 50 that interconnects a high pressure compressor 52 and highpressure turbine 54. A combustor 56 is arranged in exemplary gas turbine20 between the high pressure compressor 52 and the high pressure turbine54. An engine static structure 36 is arranged generally between the highpressure turbine 54 and the low pressure turbine 46. The engine staticstructure 36 further supports bearing systems 38 in the turbine section28. The inner shaft 40 and the outer shaft 50 are concentric and rotatevia bearing systems 38 about the engine central longitudinal axis Awhich is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion. It will be appreciated that each of the positions of the fansection 22, compressor section 24, combustor section 26, turbine section28, and fan drive gear system 48 may be varied. For example, gear system48 may be located aft of combustor section 26 or even aft of turbinesection 28, and fan section 22 may be positioned forward or aft of thelocation of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five 5:1. Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present disclosure isapplicable to other gas turbine engines including direct driveturbofans.

FIG. 2 is a perspective view of a ceramic matrix composite (CMC)component 100. In one embodiment, component 100 is, but not limited to,a gas turbine engine component, including combustor components, highpressure turbine vanes and blades, and other hot section components,such as but not limited to, airfoils, vanes, ceramic box shrouds andnozzle applications. As shown in FIGS. 2-3 , the CMC component 100 is ablade. Component 100 includes a fibrous core 120 and a ceramic matrixcomposite (CMC) shell 130 surrounding at least a portion of fibrous core120. Fibrous core 120 remains in place during operation of CMC component100. Fibrous core 120 is formed from a material that withstands the CMCcuring process and becomes a part of the final CMC component 100.Component 100 also has a root 156 and core 120 extends into the root. Itis also contemplated that in to root the core may take the shape of twochannels for the introduction of matrix precursors during CVI.

Material for the fibrous core 120 includes, but is not limited to,carbon, Al₂O₃-Sio₂, SIC, silicon dioxide (SiO₂), aluminum silicate,aluminum oxide (Al₂O₃), titanium oxide (TiO₂), zirconium silicate,silicon nitride, boron nitride (BN), and combinations thereof. Thefibrous core 120 includes braided or woven fibers. The fibrous core 120has a porosity greater than the porosity of the preform used in theformation of the CMC shell 130. For example, the fibrous core 120 mayhave a porosity that is 2 to 3 times greater than the porosity of theshell preform. The fibrous core may also include passages for coolingair in addition to the porosity. These passages may be the result ofweaving or may be formed using sacrificial materials.

The fibrous core may further include a ceramic foam portion. The ceramicfoam portion may be located centrally in the fibrous core and be atleast partially surrounded by fibers or the ceramic foam may be disposedbetween the braided or woven portion of the fibrous core and the CMCshell 130. It is further contemplated that the fibrous core may includeceramic foam at the leading edge, trailing edge or both to facilitatethe formation of sharp edge. Using a ceramic foam at these locationsoffers the advantage of being able to machine the material withoutdamaging fiber continuity.

CMC shell 130 includes a preform and a ceramic matrix. The preformincludes reinforcing fibers such as those used in the fibrous core. Insome embodiments the fibrous core and the preform employ the same typeof fiber such as SiC. The matrix material may include carbon (C),silicon carbide (SiC), silicon oxide (SiO₂), boron nitride (BN), boroncarbide (B₄C), aluminum oxide (Al₂O₃), zirconium oxide (ZrO₂), zirconiumboride (ZrB₂), zinc oxide (ZnO₂) molybdenum disulfide (MoS₂), siliconnitride (Si₃N₄), and combinations thereof. Exemplary combinationsinclude SiC fiber in a SiC matrix with a SiC/C fiber core.

As shown in FIG. 3 , component 100 is blade having a leading edge 152and a trailing edge 150. CMC shell 130 of the blade surrounds at least aportion of the fibrous core. The CMC shell 130 may completely surroundthe fibrous core 120. The sidewalls 160 of the CMC shell 130 areadjacent to the fibrous core 120 and generally joined by fibrous core120. The fibrous core 120 may include a ceramic foam 170 at the leadingedge, the trailing edge or both.

Fibrous core 120 functions as a mandrel in fabricating CMC component100. Fibrous core 120 receives or is wrapped by the reinforcing fibersof the preform. The preform includes uniaxial fiber layup, 2D wovenfabric layup, 3D weave or a combination thereof. The preform is theninfiltrated with the matrix or a matrix precursor. The matrix may bedeposited using chemical vapor infiltration (CVI) or other appropriatemethods.

The fibrous core may include sacrificial fibers or bundles ofsacrificial fibers to create cooling passages within the finished CMCcomponent 100. The sacrificial fibers may be carbon fiber, polymer fiberor a combination thereof. The composition of the sacrificial fiber willimpact when the sacrificial material is removed. Polymer materials maybe removed before CVI and carbon materials may be removed after CVI. Thedistribution and size of the sacrificial fibers or sacrificial fiberbundles may be selected by locations with a larger concentration and orlarger size near the leading edge, trailing edge, or both.

The CMC shell 130 may have a thickness of 0.03 inch (0.76 mm) to >0.10inch (>2.5 mm). The CMC shell thickness may vary over the length of theblade and may be thicker near the root compared to the tip.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application. For example, “about”can include a range of ±8% or 5%, or 2% of a given value.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A ceramic matrix component comprising a fibrouscore and a ceramic matrix composite shell surrounding at least a portionof the fibrous core, wherein the ceramic matrix composite shellcomprises a fibrous preform and the fibrous core has a greater porositythan the fibrous preform.
 2. The ceramic matrix component of claim 1,wherein the fibrous core porosity is 2-3 times greater than the porosityof the fibrous preform.
 3. The ceramic matrix component of claim 1,wherein the fibrous core further comprises ceramic foam.
 4. The ceramicmatrix component of claim 3, wherein the ceramic foam is positioned at aleading edge of the fibrous core.
 5. The ceramic matrix component ofclaim 3, wherein the ceramic foam is positioned at a trailing edge ofthe fibrous core.
 6. The ceramic matrix component of claim 1, whereinthe fibrous core comprises cooling passages.
 7. The ceramic matrixcomponent of claim 6, wherein cooling passages are located at a leadingedge of the ceramic matrix component.
 8. The ceramic matrix component ofclaim 6, wherein cooling passages are located at the trailing edge ofthe ceramic matrix component.
 9. The ceramic matrix component of claim1, wherein the ceramic matrix composite shell has a thickness greaterthan or equal to 0.03 inch.
 10. A method of making a ceramic matrixcomponent comprising forming a fibrous core having a first porosity,forming a fibrous preform on the fibrous core wherein the fibrouspreform has a porosity less than the first porosity, and forming aceramic matrix on the fibrous preform using chemical vapor infiltration.11. The method of claim 10, wherein the fibrous core comprises ceramicfoam.
 12. The method of claim 11, wherein the ceramic foam is positionedat a leading edge of the fibrous core.
 13. The method of claim 11,wherein the ceramic foam is positioned at a trailing edge of the fibrouscore.
 14. The method of claim 11, wherein the fibrous core comprisessacrificial fibers.
 15. The method of claim 14, wherein the sacrificialfibers are located at a leading edge of the fibrous core.
 16. The methodof claim 14, wherein the sacrificial fibers are located at a trailingedge of the fibrous core.